Not applicable.
Not applicable.
The field of the invention is lighting systems and more specifically a light guide that provides essentially uniform illumination from a bent surface of the guide.
Ever since development of the first light generating electrical filament, there has been a desire to control light to provide various lighting affects. One light control mechanism is a light guide or pipe. A light guide generally comprises an elongated transparent or translucent member having external surfaces. As well known in the art, when a light ray is directed within a light guide and subtends a surface of the guide, if the incident angle formed by the light ray and the surface is less than a critical angle, the light is reflected back into the guide along a trajectory that defines a reflected angle equal to the incident angle and toward another surface of the guide. Thus, if a guide is designed properly and light rays directed into a guide end are directed along suitable trajectories, in theory, the guide should facilitate total internal reflection (TIR) of the light and hence pass all of the light to an opposite end of the guide.
If the incident angles formed by light rays that subtend a guide surface are greater than the critical angle, the light is emitted through the guide surface and illuminates the area adjacent the emitting surface.
It is also known that deformities can be formed in a guide surface or within the guide itself to control the amount of light emitted from different sections of a light guide within limits. Exemplary U.S. Pat. No. 6,185,356 (hereinafter xe2x80x9cthe ""356 patentxe2x80x9d) which is entitled xe2x80x9cProtective Cover for a Lighting Devicexe2x80x9d and which issued on Feb. 6, 2001 teaches various types of illuminators that are integrally formed with surgical instruments (e.g., retractors, forceps, etc.) to provide light at desirable locations proximate the surgical implements.
In general, the ""356 patent teaches that guide surface deformities such as textured surfaces, particles within the guide, etc., scatter or xe2x80x9crandomizexe2x80x9d light rays within a guide. Thus, guides can be constructed to both deliver right rays and to then disperse the light rays at desired locations along the guide length. To deliver light, a guide section can be designed to facilitate TIR. To disperse light rays and provide light at specific locations, deformities are formed in the guide that alter light ray trajectories and thereby cause at least a portion of the rays passing through the guide to travel along trajectories forming incident angles with guide surfaces that are greater than the critical anglexe2x80x94hence causing the rays to be emitted from the guide surface.
The ""356 patent also generally recognizes that a uniform lighting effect can be provided by varying the deformity pattern along a guide surface. For instance, assume that an elongated light guide includes a first segment adjacent a light source and a second segment adjacent the first segment, that the lengths of the first and second segments are identical and that a light source directs 10 units of light into a distal end of the first segment opposite the second segment. Also assume that deformities along the first segment cause three units (e.g., 30% of the total light from the source) of the light to refract out of the guide surface so that only seven units of light are passed on to the second guide segment. Here, if the second segment includes deformities having light refracting properties similar to the first segment, approximately 30% of light entering the second segment (i.e., approximately 2.3 units) is refracted out the surface along the second segment length and, therefore, the intensity of light emitted along the second segment is less than along the first segment.
However, if deformities are provided in the second segment surface that cause approximately 43% of the light entering the second segment to be emitted along the second segment length, approximately three units of the seven units entering the second segment are emitted along the second segment surface and hence similar quantities of light are emitted from the first and second guide segments. This principle of non-uniform deformities can be applied to a large number of small adjacent guide segments to provide a substantially uniform lighting affect.
In the case of a textured surface, the randomizing texture can be formed on either or both of an emitting guide surface (i.e., a surface from which light is intended to be emitted) and a primarily reflecting surface opposite or at least substantially opposed to the emitting surface. In the case of a textured emitting surface, the texture alters the angle of the surface subtended by the light rays so that the incident angle with the small subtended surface is greater than the critical angle and light is emitted. In the case of the textured reflecting surface, the texture causes reflected light rays to travel toward the emitting surface along trajectories that form incident angles with the emitting surface that are greater than the critical angle and hence, similarly, cause light ray emission.
The ""356 patent also recognizes that a textured surface can be formed by molecularly bonding some type of coating material to a guide surface. The molecular bonding process, in effect, causes small hills and valleys (i.e., texture) on the bonded guide surface. The bonding and texturing process may include a painting or spraying procedure followed by a curing period, other material deposit type processes, forming of a guide about a thin reflective member (e.g., a plastic member), etc.
In addition, the ""356 patent recognizes that the coating material bonded to a guide may be light opaque so that light rays are not emitted from the coated surface of the guide but rather are redirected back into the guide. Here, where the coating material has a specific color, the color will affect the appearance of the light emitted from the emitting surface. For instance, a white paint coat on a reflecting surface affects the appearance of the emitting surface.
While the ""356 patent teaches some useful concepts, the ""356 patent has some shortcomings when used to provide certain effects. First, while deformity variance along a guide length can be provided to cause essentially uniform illumination from each guide segment, where the deformity variance is too great, the visual effect of the different guide segments will often be very different. Thus, for instance, one guide segment having ten times the deformities as another segment may cause a similar quantum of light to escape the guide along a similar length but the deformities may cause a different light pattern. This variable appearance problem is particularly acute in the case of long illuminating surfaces where distal guide segments are a relatively long distance from a light source than are other segments and the degree of deformity necessary to facilitate a uniform appearance is excessive.
Second, the ""356 patent fails to teach a configuration having a uniformly appearing emitting surface that has both a linear and a curved component. In this regard, when a light source directs light through a linear guide section and then into a curved guide section adjacent the linear section, and a reflecting coating is provided on a guide surface opposite an emitting surface, often xe2x80x9cshadowsxe2x80x9d or xe2x80x9cdark spotsxe2x80x9d will appear when the emitting surface of the curved section is viewed. This xe2x80x9cspottingxe2x80x9d phenomenon occurs because light exiting the linear section of the guide is generally along trajectories parallel to the guide length and hence the rays shoot past the beginning and middle part of the curved section, subtend the ending part of the curved section and non-uniformly illuminate the curved section. The ""356 patent fails to recognize this phenomenon as a problem, and instead, teaches guide configurations that either geometrically do not have the spotting problem or that take advantage of the problem. In this regard, the ""356 patent teaches two relevant configurations.
First, in some embodiments (e.g., the illustrated retractor) the ""356 patent accepts the curved illumination problem and designs illuminators that take advantage of a small radius curve to emit light from the curved surface toward an area of interest. In this case the guide segment leading to the curved surface and the segment downstream of the curved section emit little if any lightxe2x80x94an acceptable affect given the nature of a retractor or other type of surgical tool.
Second, in some embodiments the ""356 patent teaches guides (e.g., a ring-shaped rope) having substantially curved surfaces that do not include a reflective coating. In these cases the ""356 patent relies primarily on deformities within the guide member (i.e., reflecting particles) or deformities within the guide surfaces themselves to cause light emission. Thus, here, as in the case of a long and narrow guide member, light emission is a function of the number and type of deformity and guide member curves and related surface juxtapositions are essentially irrelevant. While this solution provides a relatively tight curved emitting surface, unfortunately, without a reflective surface opposite a desired emitting surface, at least a portion and, in many cases, a large percentage (e.g., 50%) of guide light is emitted from the surface opposite the desired emitting surface and light intensity is appreciable reduced. In addition, it is doubtful that, even with a careful selection of surface deformity variance, that a uniform appearance can be attained via texturing alone due to the xe2x80x9cspottingxe2x80x9d phenomenon described above.
One other attempt to provide a bent light configuration is described in U.S. Pat. No. 4,907,132 (hereinafter xe2x80x9cthe ""132 patentxe2x80x9d) which is entitled xe2x80x9cLight Emitting Panel Assemblies and Method of Making Samexe2x80x9d which issued on Mar. 6, 1990. The ""132 patent teaches a woven fiber optic material that includes bends formed in the optic fibers at discrete locations to allow light to be emitted therefrom. The fibers are woven so tightly that, despite the fact that each fiber only emits light from its bends, the overall effect is substantially uniform light emittance.
One obvious problem with this solution is that, despite attempts to weave an extremely fine material, it is extremely difficult to provide a material that, when illuminated, effectively renders the separate fiber bends indistinguishable. Even if a material could be provided that is tight enough to render adjacent fabric bends indistinguishable, the material would likely be far too expensive to manufacture for most applications.
Thus, there is a need for an illuminator that is simple and inexpensive to manufacture and that provides a uniformly illuminated relatively tightly curved or bent emitting surface and an adjacent linear surface where the emitting surface has a uniform appearance.
The invention includes a lighting apparatus for providing a substantially uniformly illuminated light emitting surface, the apparatus comprising first and second light sources generating flux patterns including light rays that diverge about first and second central light rays, respectively and a light guide member having substantially straight first and second en sections and a curved section, the first end section having a proximal end and a distal end and formed about a first light axis, the second end section having a proximal end and a distal end and formed about a second light axis, the curved section including first and second ends that are linked to the distal ends of the first and second end sections, respectively, the guide forming a front surface and an oppositely facing textured back surface along each of the end sections and the curved section, the curved section forming a bend such that the back surface is concave and the front surface is convex along the curved section length, at least a portion of the back surface tapered toward the first light axis in the direction from the proximal end to the distal end of the first end section. Here, the first light source is juxtaposed such that the central light ray is directed along the first light axis and the second light source is juxtaposed such that the central light ray is directed along the second light axis.
In one embodiment of the invention the degree of taper along the first end section increases from the proximal end to the distal end. In a more specific embodiment at least a portion of the back surface tapers toward the second light axis in the direction from the proximal end to the distal end of the second end section and the degree of taper along the second end section increases from the proximal end to the distal end. Even more specifically, in an embodiment the rate of taper increase is constant along the lengths of each of the first and second end sections.
In one embodiment the first end section includes X equi-length segments and the degree of taper changes N degrees along each of the X segments. Here, N may be between 1 and 5 degrees.
The first end section may form a proximal end width dimension between the front and back surfaces and the length of each equi-length segment may be between three and seven times the proximal end width dimension. More specifically, the length of each equi-length segment may be approximately five times the proximal end width dimension.
In some embodiments a width dimension between the back and front surfaces is uniform along the length of the curved section. In addition, a texture may be provided along at least a portion of the front surface. Moreover, the guide may form top and bottom surfaces and at least a portion of each of the top and bottom surfaces may be textured.
Some embodiments further include a coating layer on the back surface and the texture is provided on the back surface by a molecular bond between the coating layer and the back surface. More specifically, the coating layer may include a plastic member and the plastic member may be white.
In some embodiments the first and second light axis form an angle between 60 degrees and 130 degrees. In a particularly advantageous embodiment the first and second light axis form an angle of approximately 90 degrees.
The invention also includes a lighting apparatus for providing a substantially uniformly illuminated light emitting surface, the apparatus comprising a light source generating a flux pattern including light rays that diverge about a central light ray and a light guide member having a substantially straight end section and a curved section, the end section having a proximal end and a distal end and formed about a light axis, the curved section including first and second ends and linked at the first end to the distal end of the end section, the guide forming a front surface and an oppositely facing and textured back surface along the end section and the curved section, the curved section forming a bend such that the back surface is concave and the front surface is convex along the curved section length, at least a portion of the back surface tapered toward the light axis in the direction from the proximal end to the distal end. Here, the light source is juxtaposed such that the central light ray is directed along the light axis.
Here, the degree of taper may increase from the proximal end to the distal end. In addition, the rate of taper increase may be constant along the length of the end section. Moreover, the end section may include X equi-length segments and the degree of taper may change N degrees along each of the X segments.
In one embodiment the end section forms a proximal end width dimension between the front and back surfaces and the length of each equi-length segment is approximately five times the proximal end width dimension.
In some embodiments the end section is a first end section and the light source is a first source, the apparatus further including a second end section and a second light source, the second end section including proximal and distal ends and formed about a second light axis, the second light source generating a flux pattern including light rays that diverge about a central light ray, the second end section linked to the second end of the curved section and the second light source is juxtaposed such that the central light ray of the second source is directed along the second light axis.
The front surface may be substantially parallel to the light axis along the end section. In the alternative, at least a portion of the front surface forms an angle with respect to the light axis.
These and other aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention.